The Carbon Cycle

All living things are on Earth are carbon based life forms, carbon is the essential element for all living things.

On Earth, inorganic carbon (CO₂) can be found:

1. in the atmosphere.
2. dissolved in oceans.

Organic carbon is found in only one place:

1. as part of the bodies that are living things.

Cycling

Autotrophs:

– conduct photosynthesis; use light energy from the sun and water from the soil or ocean to combine CO₂ into complex organic molecules

6 CO₂ + 6H₂O + light energy -> C₆H₁₂O_{6 (}glucose) + 6 O₂

– includes land and aquatic plants, algae and some bacteria

All living things:

– perform cellular respiration, which converts glucose into CO₂ and H₂O molecules

C₆H₁₂O₆ (glucose) + 6 O₂ -> 6 CO₂ + 6 H₂O + energy for cell

Complementary Processes

– the carbon that they use is repeatedly cycled through both processes
– this cycling of carbon is called the Carbon Cycle

Carbon Reservoirs

Reservoirs of Inorganic Carbon:

– atmosphere (CO₂ gas; 0.03%)
– oceans (dissolved in water or part of the shells of living things)
– Earth’s crust (rocks)

Reservoirs of Organic Carbon:

– bodies of living things (released by decomposers when organism dies)
– bogs (little decomposition; form coal)
– ocean floors (little decomposition; form oil)